1. Field of the Invention
The present invention relates a pulse width modulation (hereinafter also referred to as “PWM”) amplifier that generates a triangular wave and performs PWM amplification of an input signal based on the triangular wave, and more particularly to a PWM amplifier configured to reduce unwanted radiation from an output signal thereof, which can cause EMI (electromagnetic interference).
2. Description of the Related Art
Conventionally, a PWM amplifier is known which generates a triangular wave and performs PWM amplification of an input signal based on the triangular wave such that unwanted radiation from an output signal, which can cause EMI, is reduced.
A PWM amplifier of this kind has been proposed e.g. by Japanese Patent Publication (Kokoku) No. H07-85524, which generates a triangular wave whose frequency has been modulated with a random signal and performs PWM amplification of an input signal based on the triangular wave, thereby reducing unwanted radiation from an output signal thereof, which can cause EMI.
For modulation of the frequency of the triangular wave with the random signal, however, the conventional PWM amplifier requires provision of not only a triangular wave-generating circuit but also a random signal-generating device (oscillator) and an FM (frequency modulation) circuit for modulating the frequency of the triangular wave with the random signal from the random signal-generating device. This results in increased manufacturing costs.